In addition to some decline in cognitive abilities, there is often some reduction in reaction time, and when combine all this with some loss in field of vision in some cases, caution may be a good thing.
Someone mentioned use of trikes… seems like a good idea but even with a trike, descending on a hilly road with blind turns is always going to be risky. Unlike in my younger days, I’m not adversely against slowing down, especially around blind turns.